superjamie

The configuration tool allowed users to try for 1GHz but it definitely wasn't achievable on all boards. I had a first-batch 256MiB RAM Pi 1 (which I bought the week they were released in 2012) and a later 512 MiB Pi 1, both of which could not reliably go past 900MHz. I've spoken to other Pi 1 owners who could achieve 950MHz or 1000MHz, and one owner whose board couldn't even get past 850MHz reliably. If you had a Pi 1 reaching 1150MHz, you were very lucky and your experience was definitely not typical of most users.

It was the limit of manufacturing capability at the times of release. The first Pi was released April 2012, the B+ was released July 2014, and the Zero was released November 2015. In 2012, Broadcom could only make the SoC well enough that the ARM1176JZF-S could reliably reach 700MHz. Some units could be overclocked with good results but many could not. By the end of 2015 - almost four years later - they had improved the precision of the manufacturing process so that 1000MHz was possible and reliable on all chips.